In the right hands sunlight is a medicine. Throughout history it has been used to prevent and cure a wide range of diseases, and a few doctors still use its therapeutic properties to good effect. However, at the present time it is widely held amongst certain sections of the medical profession and the population at large that the damaging effects of sunlight on the skin far outweigh any benefits. Public health campaigns reinforce this message in an attempt to curb the annual increase in skin cancers. Any illusions about tanned skin being a sign of health or providing more than minimal protection to further exposure to the sun's rays seem to have been dispelled.

Sunlight may cause skin cancer, but there is also evidence that it could prevent a number of very common and often fatal diseases: breast cancer; colon cancer; prostate cancer; ovarian cancer; heart disease; multiple sclerosis; and osteoporosis. When combined, the number of people who die from these conditions is far greater than the number of deaths from skin cancer; which is why the current bias against sunlight needs, in my opinion, to be redressed.

But before going any further, let me explain how I came to write The Healing Sun. Usually books of this kind are written by doctors of medicine, or medical journalists, and not doctors of engineering. However, my background is a little unusual in that for many years, while I was designing or evaluating what could broadly be called solar energy technologies of one form of another -- solar collectors; equipment for use in spacecraft; and energy-efficient buildings -- I was also studying complementary medicine. Working alongside architects on one particular project I became aware of a 'lost' tradition of designing sunlit buildings to prevent disease, rather than to save energy, and I became interested in the healing powers of sunlight.

I began to study the history of sunlight therapy and found that the physicians who practiced this ancient healing art, and the architects and engineers who supported them in their work, used sunlight very differently from the way many of us do today. In comparing this with some of the latest findings from medical research on sunlight and health I have, as you will see, come to some rather controversial conclusions.

The sun transmits energy in the form of electromagnetic waves: radio waves; microwaves; infrared radiation; visible light; ultraviolet radiation; and x-rays. Only a small amount of the sun's energy reaches us, as most of it is filtered out by the earth's atmosphere, so solar radiation at ground level is composed of visible light, and ultraviolet and infrared waves. Until the latter part of the 19th century it was thought that the 'heat' of the sun -- what we now know to be the infrared rays -- caused sunburn. Then scientists discovered that it is the ultraviolet component of sunlight which causes the skin to tan, and they began to use ultraviolet radiation on skin diseases. They then found that they could get better results with sunlight itself.

Sunlight therapy has a habit of being discovered and then falling from favor, and when this happens it disappears almost without trace, sometimes for hundreds of years. It was very popular at the beginning of the 20th century, but has since seen a dramatic reversal in its fortunes with the result that a great deal of knowledge about the healing powers of sunlight has been ignored or forgotten.

Did you know, for example, that sunlight kills bacteria and is quite capable of doing so even when it has passed through window glass? Also, were you aware that sunlit hospital wards have less bacteria in them than dark wards, and that patients recover faster in wards which admit the sun? As infections actually caught in hospital are now the fourth most common cause of death after heart disease, cancer and strokes, it is worth bearing in mind.

The human race evolved under the sun, and the sun's healing powers have been worshipped for thousands of years. In fact, your forebears were probably better informed about the sun's healing properties than you are: people hold very different views on sunbathing depending on when they were alive and where they happen to live. Take, for example, a typical well-educated resident of Essen or any industrial city in Germany in the 1920s. Let us say he had served in the German army during the Great War, was wounded, and returned home having recovered from his injuries. Someone in these circumstances would have held sunlight in much higher regard than many of us do today. He would probably been aware of the scientific discoveries that had been made about light in the years immediately before the war: in 1903 the Nobel Prize for medicine was awarded to the Danish physician, Niels Finsen, in recognition of his success in treating tuberculosis of the skin with ultraviolet radiation.

Then again, during the war, military surgeons may have used sunlight to disinfect and heal his wounds at a sunlight therapy clinic in the Black Forest, or a similar institution in the Swiss Alps. Had he contracted tuberculosis on his return to Germany, sunlight therapy, or heliotherapy as it became known, might have been used to aid his recovery. The physicians who supervised the treatment of his wounds or tuberculosis would have paid very close attention to the way he responded to sunlight and, in particular, how well his skin tanned. In those days, the deeper the tan, the better the cure.

Sunbathing for health in this way required the services of skilled physicians who knew precisely the conditions most favorable for their patients: the best time of day to expose them to the sun; the best time of year; the correct temperature for sunbathing; what foods to give; how much exercise to allow in each case; which type of cloud cover would let enough of the sun's rays through to cause burning and so on. Then, as now, the overriding concern was to prevent burning; but it was the actual process of tanning which dictated the progress of the treatment and whether or not it was successful.

During the 1930s sunbathing was encouraged as a public health measure. Diseases such as tuberculosis and rickets were common in the industrial cities of Europe and North America at this time and it became accepted practice to expose anyone considered susceptible to either of them to sunlight. So the sun was used to prevent disease as well as cure it. Also, architects were introducing sunlight into buildings to prevent the spread of infection because, as we have already seen, it kills bacteria. They designed hospitals and clinics for sunlight therapy and even included special window glass so that patients could tan indoors during bad weather -- ordinary window glass prevents tanning because it acts as a barrier to ultraviolet radiation.

In marked contrast to our German friend of the 1920s, someone living in Britain today would have a very different impression of sunlight and its effects on the human body. The received wisdom is that there is no such thing as a safe or healthy tan, and that a tan is a sign of damaged skin trying to protect itself from further injury. Children and adults are advised to protect themselves from the sun; particularly during periods of sunny weather during the spring and early summer. They are to avoid the sun between the hours of 11 am and 3 pm and protect themselves with T-shirts, hats and sunscreens. As you can see, there has been a complete reversal in thinking on the subject.

Reasons for the current antipathy towards the sun are not hard to find. After the Second World War, improvements in housing and nutrition led to a marked decrease in the incidence of the very diseases which sunlight had been used to treat. When antibacterial drugs such as penicillin and streptomycin became widely available in the 1950s medical practice changed out of all recognition. These new drugs offered the prospect of rapid cures for a wide range of infections, and so the hygienic and medicinal properties of sunlight were no longer considered to be as important as they had been. Sunlight therapy became unfashionable, and was soon relegated to the position of historical curiosity.

More recently there has been a great deal of emphasis on the harmful effects of sunlight. There is now a 'hole' in the ozone layer to worry about, as well as a year-on-year increase in the incidence of skin cancer. Sunlight is undoubtedly a powerful accelerator of skin aging, and can trigger cancer in susceptible individuals but, paradoxically, it is essential to our health. The human body needs sunlight to manufacture vitamin D by synthesizing it in the skin.

The optimal level of vitamin D for health is not known, and so the amount of sunlight exposure needed to perform this vital function is still very much open to question. What this means is that warnings about sunlight being essentially harmful need to be treated with caution. Sunlight may cause skin cancer but, there is evidence that the sunlight could be crucial in preventing a number of diseases that are associated with low levels of vitamin D. Also, relatively little importance has been attached to the influence of nutrition in the genesis of skin cancer. Yet the limited amount of research carried out on the subject shows that what you eat determines how your skin responds to sunlight. The proportion of fat in your diet, together with the vitamin and mineral content of your food, could decide how likely you are to sustain skin damage in the sun.

The medical literature on sunbathing is contradictory: one field of investigation highlights the benefits while another stresses the dangers. One of the more unfortunate developments in modern medicine is a trend towards specialization. In these circumstances it is difficult not to be unduly influenced by the views of experts in one field or another and miss the wider picture. It becomes much more difficult to see the wood for the trees or, rather, the sunlight through the trees.

Indeed, to fully appreciate the beneficial effects of sunlight it is sometimes advantageous to put aside conventional medical thinking altogether and look to other traditions of healing. Sunlight, when used as a medicine, does not lend itself to the western reductionist method of analysis: trying to fathom its therapeutic effects at a molecular level, to the exclusion of all else, may not be the best way to unlock its secrets.

When sunlight has been valued as a medicine, architects have often produced buildings which admitted the sun's rays. But when sunlight is out of favor with doctors, as is the case at present, there is little incentive for architects to make provision for it in their buildings. There has been a tendency for therapeutic properties of sunlight to be held in much higher regard during periods when prevention was considered to be as important as cure. In these circumstances the demarcation between physician and architect was often much less marked than is the case today. In the past, architects were encouraged to have some knowledge of medicine.

During the last thirty years the hygienic and medicinal properties of sunlight have had little influence on the building professions. Where solar architecture has been adopted it has been for the purposes of energy conservation rather than health; even though it has long been recognized that getting sunlight into buildings has a favorable impact on the well-being of occupants.

Sunlight penetration into buildings is now regarded as 'beneficial' or 'desirable' but this aspect of design still receives a relatively low priority. Indeed, the benefits of getting sunlight into buildings, other than psychological, would not be obvious to anyone reading the current literature on building design. As we now spend so much of our time indoors, I believe the advantages of living or working in a sunlit space need to be more widely studied and appreciated than is the case at present.

Sunlight therapy was a medicine of the pre-antibiotic era, when infectious diseases were commonplace and the only defense against them was a strong immune system. Since then, for about fifty years, tuberculosis, pneumonia, septicemia and a host of other potentially fatal illnesses have been kept under control by antibiotics. Unfortunately an increasing number of bacteria are becoming resistant to drugs and there are signs that the development of new antibiotics is falling behind the ability of organisms to adapt and acquire resistance. If matters do not improve, then therapies which increase our natural resistance to disease may receive rather more attention than they have in recent years. The emergence of resistant bacteria may also come to have an influence on building design.

Please note: There are medical conditions which are made worse by exposure to sunlight, and some drugs, such as antihistamines, oral contraceptives, antidiabetic agents, tranquilizers, diuretics and a number of antibiotics, increase sensitivity to the sun. Anyone about to embark on a program of sunbathing should check with their doctor if they are in any doubt about their health or any medicines which they are taking.

This article is excerpted from the book:

About the Author

Richard Hobday, MSc, PhD is a member of the British Register of Complementary Practitioners and has studied traditional Chinese Medicine and Chinese exercise systems in China. Dr. Hobday has many years experience of solar design in buildings and is a leading authority on the history of sunlight therapy. Visit the author's website at http://www.healingsun.co.uk